Scott's Photographica Collection

How to Assemble Color Separation Photographs in Photoshop

The separation photographs that appear on this page were taken with a Nikon FM camera on
T-Max 400 35mm film. The individual frames were exposed consecutively
through red (#25), green (#58) and blue (#47B) tri-color filters. The negatives were then
scanned and inverted to positives by the scanner software. The procedure
that's described below can be applied without change to negative images as well
as positives. Of course, if you are working with negatives, at least as
the final step you will want Photoshop to invert your final image to a positive.

With Photoshop it seems that no matter what you want to accomplish, there is
more than one way to skin the proverbial cat. Having experimented with a
variety of ways to assemble separations in Photoshop, I've settled on the
following procedure as the simplest.

Other methods that I've explored included copying separations to layers and
using the Merge Channels command. You may find one or both of these
approaches useful depending on the nature of your separations and the look that
you want in your final image.

The procedure begins by using the Load Files into Stack script to open the
separations
in Photoshop. This is not necessary; you can open your separations
individually instead, but what the script has to its advantage is that it will
attempt to align, or register the separations for you.

Once the separations are assembled you'll have the opportunity to
manually adjust registration, and this is easy to do. However, you won't be
able to rotate the individual channel images; they can only be moved vertically
and
horizontally. The Load Files into Stack script will attempt to apply rotation
to the individual images. It is common for separations to be out-of-square
with each other so this is a real time saver. If your separations require
rotation to achieve precise registration and you don't use the load script, or
if the script is incapable of
achieving good registration because of problematical separations, then you
will need to rotate them manually.

I haven't illustrated a method for manual rotation on this page but here is a
brief description: Create an image with three layers. Each layer
should be one of your separations. Make the top two layers visible and
hide the bottom layer. Reduce the opacity of the top layer.
From the Edit menu, select Transform/Rotate. Rotate the lower of the two
visible layers and as you do, with the appropriate opacity setting you should be
able to see the images in both layers. Align the lower image with the
upper. When the images are square (ignore lateral and vertical
misalignment), hide the second layer, make the bottom layer visible and rotate
that layer to align its image with the top layer. When the images are
square, set the opacity of the top layer back to 100 percent. Now proceed
as described below but bypass the load steps.

So let's begin...

Use the Load Files into Stack script to load the separations.

Browse to locate your separations.

Select your files and click Open.

On the way out, remember to check Attempt to
Automatically Align Source Images

Photoshop creates a new image and assigns a name, in this case Untitled1.
As the images are loaded, Photoshop will attempt to align (register) them.
Accuracy depends on the quality of the separations. Often you will want
to tweak registration, and you can do so later. Here we see Untitled1 and
its three layers: Scan10010, which is the red record; Scan10011, the green; and
Scan10012, the blue.

Click on the top layer in the Layers palette to make it active. In the image above, the top
layer, Scan10010.TIF is highlighted indicating that it's the active layer. Actually, it doesn't matter which layer
is selected at this step, but starting with the top layer will help keep things
organized as we proceed.

Select All

Copy the selection to the clipboard. The layer that was
previously made active will be copied.

Create a new image. This is to be the assembled color image.

Again, Photoshop will assign a default name, in this case Untitled-1.
This name is different from the separation image which was named Untitled1.
Your results may differ. Now is a good time to assign a name to
the final color image. This is illustrated below.

This new image will become the final color assembly so give it a
descriptive name.

It's important to change the color mode from grayscale to RGB Color.
If you are working with RGB separations don't change the color mode from RGB.

Don't alter the width or height. The other attributes: resolution,
color profile, bits and pixel aspect ratio can be modified.

Notice that preset changed from clipboard to custom.
Photoshop is indicating that the image description was customized by the
change to color mode or by changes the user may have made to other attributes.

Make the new image active (candy_and_kites) and switch to
the Channels palette.

Click on the red channel to make it active.

Paste the image that was previously copied to the clipboard to the red
channel by selecting Paste from the Edit menu.

The red record has been pasted to the red channel.

Switch back to the separation image and make the Layers palette visible
again. Click on the second layer which in this exercise is the green
record.

Copy the second layer to the clipboard. It's not necessary
to select the image again before copying.

Switch back to the new color image. Switch from the Layers to the
Channels palette and click on the green channel. Edit/Paste the contents
of the clipboard to the green channel.

Switch back to the separation image and make the Layers palette visible
again. Click on the third layer which in this exercise is the blue
record.

Copy the third layer to the clipboard. It's not necessary
to select the image again before copying.

Switch back to the new color image. Switch from the Layers to the
Channels palette and click on the blue channel. Edit/Paste the contents
of the clipboard to the blue channel.

Click the eye next to the RGB channel to view the
full-color image.

And here it is, the full-color assembly. However, registration is not yet perfect. Color
fringing is
particularly noticeable when the image is magnified. We'll improve
registration in the following steps.

Magnify the image to check for color fringing. Fringing is obvious in the sign and
door frame, i.e., the stationary areas of the subject. The flags and Santa
Claus moved between exposures so we won't (don't want to) attempt to register
them.

Individual channel images can be moved around with the Move tool. To
move a channel image, select its channel. In this
example, I selected the red channel. Notice that it's highlighted. I
also made the green channel invisible (unselected its eye) and made the blue
channel visible by selecting its eye.

Use the Move tool and/or the arrow keys on your keyboard to reposition the
image. The arrow keys allow you to make very fine adjustments.

The red and blue images are now in registration.

Next align the green image with the blue. Select the green channel. The green and blue channels should be visible (eyes
selected) and the red channel should not (eye unselected).

Use the Move tool and/or the arrow keys on your keyboard to reposition the
image. The arrow keys allow you to make very fine adjustments.

The green and blue images are now in registration.

At 100 percent magnification it appears that the three
images are in registration.

It's not necessary to align layers in the sequence given above, i.e.,
start with blue and red. Start with the combination of colors that
allows you to most easily view the subject's edges. You can also make all
three channels visible rather than view two at a time. Whatever works best
with your image is the way to go.

The final color assembly.

Related Information

• A variety of color separation cameras and color photographica can be found in
the Color Photographica section.